In synchronous type communications networks and more particularly TDM (Time division multiplex) type networks, a multiplexing technique is used to enable a transmitter to transmit data from one or more channels working at a certain bit rate in a transmission channel of a higher bit rate associated with a communications network.
The bandwidth available in the transmission channel associated with a communications network is subdivided into several synchronous virtual channels or VCs corresponding to time slots.
Each virtual channel corresponds to a set of bits (also called a sample here below) used by a transmitter to transmit data. A transmitter can use a set of virtual channels.
A full synchronous data-processing cycle (SDPC) is formed by all the samples of each of the virtual channels available on the communications network. The SPDC cycle is characterized by the frequency at which a transmitter can write to a same virtual channel. The SPDC cycle possesses a finite number of virtual channels. It is therefore necessary to optimize its use in order to increase the useful bit rate of this synchronous network.
In a first classic technique, a device manages the total bandwidth of the transmission channel associated with the network in distributing a set of virtual channels among the different transmitters of the network. A transmitter may, for example, make a request to this device, indicating its needs in terms of resources, and the device will reserve a number of virtual channels for it accordingly.
However, one drawback of this prior art technique is that a transmitter of the network can ask for more resources than it really needs. There is therefore a loss of bandwidth, with certain sources reserved for a given application remaining unused throughout the time when this application is being implemented. This is especially true when the granularity of reservation of the resource is greater than the granularity of the data transmitted by a transmitter of the network or when the granularity of reservation of the resources greater than the quantity of data sent out by a transmitter of the network in a transmission cycle: for example, when the system permits blockwise reservation of N*X bits per transmission cycle and when the transmitter node sends a maximum of M words of X bits per transmission cycle, with M<N.
To make the management of the bandwidth of the transmission channel more efficient and thus improve the performance of the communications synchronous network, a second prior art technique, described in the patent document WO2005/006112, presents a MAC (media access controller) protocol implementation in a TDMA (time-division multiple access) type network having a master node and several slave nodes. This second known technique manages the time slots of the frame dynamically, in creating time slots with a granularity of one bit. When a transmitter sends a request to the master node, the master node allocates a set of one-bit time slots to the transmitter, thus enabling the most efficient use of the total bandwidth of the network. To manage these sets of time slots efficiently, a header, are designated as a “sync slot” is used for each of the sets so that a receiver can get synchronized with the appropriate set.
However, one drawback of this second prior art technique relies on the addition of a header which uses a part of the useful bandwidth. Thus, when the number of concurrent applications implemented within the network is great, the loss of resources is high.
Besides, another drawback of this second prior art technique is that, when an application requires only few resources, the size of the header is disproportionate to the rest of the data to be transmitted.